It appears that Facebook has since broadened its test group. Screenshots shared by the Twitter account @iOSAppChanges show the feature working on an iPhone running the Italian carrier TIM.

Facebook's message expiration feature can be enabled from a dedicated "Disappearing Messages" tab on a contact's page in the Messenger app, according to the screenshots. Messages for a conversation thread can then be set to expire after 1 minute, 15 minutes, 1 hour, 4 hours, or 24 hours.

While Facebook is clearly following Snapchat's lead on ephemeral messaging, Messenger's approach to giving controls over when messages expire is quite different. All messages on Snapchat disappear immediately after they're viewed, although you have the ability to replay each message once.

Other additions to Messenger, including a "Shared Links" view for all of the web links shared in a thread, are also present in the screenshots. Mentions of a "secret chat" option and the ability to create events in Messenger also appear in a list of "hidden" features shared on Pastebin.

It's unclear when or if Facebook has plans to introduce any of these feature it's testing more broadly. The company wasn't immediately available to comment.